On the map itself you can see some controls:

click the magnifying glass icon on the map and move your mouse over a marker - it will automatically zoom on your selection move the map by clicking on the direction arrrows, or drag it by left clicking and dragging the mouse click to toggle the selector box control on and off. Once visible, drag the selector box over the area you want to search. You can change the size of the selector box by dragging its bottom right hand corner. To search click on the magnifying glass icon in the selector box. Reset the map by clicking on the top left hand icon in the box you can zoom the map by using the zooming scale